This in relates generally to a one piece plastic carbonated beverage container with a looted base structure; and particularly, a container of this type molded with a reduced amount of plastic material while maintaining an extended stance of each foot. These containers are usually, although not exclusively, made from a polyethylene terephthalate (PET) polyester material using a blow molding process that biaxially orients and sets its molecular structure.
A major difficulty in a filled and sealed carbonated container is controlling and minimizing the distortion of the looted base structure from the pressure created by the carbonated beverage. Under normal conditions this pressure can exceed 75 PSI (5 bar). Uncontrolled distortion can lead to a variety of problems.
One problem is poor container stability from a "rocker bottom" where the central region of the base bulges downwardly to a point where the supporting feet can not simultaneously contact a supporting surface. In this case the container is supported in a tilted somewhat unstable position by the central region and two of the feet.
Another problem is container damage from buckling, creases, bumps and bulges in the feet and sidewall areas. In some cases this can lead to structural damage from concentrated stresses; in other cases this can lead to an aesthetically unpleasing shape. Containers with concentrated stresses may burst if subjected to impact.
Another problem is an inconsistent fill level line position created by an inconsistent expansion of the container, most of which occurs in the base structure area. Fill line position consistency is important to consumers in that consumers often believe a fill level below standard signifies an underfilled or unsealed container.
Also to be considered is that an untilled container must be able to stand upright in the filling machinery. Containers that fall over during conveying will adversely affect the cost and efficiency of filling operations. Stability is improved with a wide stance of the feet of the base structure. Another consideration is maximization of the area of each foot pad in contact with the conveyor or other supporting surface. Small foot pads tend to become caught and fall over in the machinery.
The prior art describes many examples of one piece plastic carbonated beverage containers with footed base structures. To achieve success, such containers depend on a relatively heavier container with substantial material thickness in the base structure area. The approach uses mass to resist distortion, but heavier containers tend to be costly to produce. When these containers are made with less material many of the problems mentioned above occur. Those containers which tend to be lighter in weight tend to reduce the stance of the feet or reduce the area of each foot pad which often create stability problems before and after filling.
It is therefore desirable to provide a footed carbonated beverage container of reduced material weight with a wide stance of the base structure feet and a large foot pad area while controlling and manipulating the expansion and distortion of the base from the beverage carbonation pressure so as not to adversely affect the consistency of fill line position, aesthetic appearance, and stability or to create excessive concentrated stresses.